U.S. patent number 8,092,545 [Application Number 11/209,931] was granted by the patent office on 2012-01-10 for knee arthroplasty prosthesis method.
This patent grant is currently assigned to Zimmer, Inc.. Invention is credited to Thomas M. Coon, Donald M. Smucker, Alfred J. Tria, Jr., Richard R. Van Zile.
United States Patent |
8,092,545 |
Coon , et al. |
January 10, 2012 |
Knee arthroplasty prosthesis method
Abstract
A knee arthroplasty prosthesis includes a femoral component
having multiple pieces with engagement means provided for engaging
various pieces of the femoral component to one another following
their insertion in the incised area of the femur. A tibial
component includes multiple pieces designed for assembly following
positioning in the incision. The tibial component includes a Morse
taper cavity on one piece of the tibial component and a Morse taper
extension on another member of the component for receipt
therein.
Inventors: |
Coon; Thomas M. (Redding,
CA), Tria, Jr.; Alfred J. (Princeton, NJ), Smucker;
Donald M. (Perrysburg, OH), Van Zile; Richard R. (Bryan,
OH) |
Assignee: |
Zimmer, Inc. (Warsaw,
IN)
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Family
ID: |
27757712 |
Appl.
No.: |
11/209,931 |
Filed: |
August 22, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050283250 A1 |
Dec 22, 2005 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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10370154 |
Feb 19, 2003 |
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60358174 |
Feb 20, 2002 |
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Current U.S.
Class: |
623/20.32;
623/20.34 |
Current CPC
Class: |
A61F
2/38 (20130101); A61F 2/389 (20130101); A61F
2/4637 (20130101); A61F 2002/30387 (20130101); A61F
2002/30515 (20130101); A61F 2250/0084 (20130101); A61F
2002/30433 (20130101); A61F 2220/0041 (20130101); A61F
2/3859 (20130101); A61F 2002/30405 (20130101); A61F
2002/30604 (20130101); A61F 2220/0025 (20130101); A61F
2002/30878 (20130101); A61F 2002/4631 (20130101); A61F
2220/0033 (20130101); A61F 2002/30884 (20130101); A61F
2002/30332 (20130101); A61F 2002/30892 (20130101); A61F
2002/30492 (20130101); A61F 2002/30339 (20130101); A61F
2002/30797 (20130101); A61F 2002/3079 (20130101); A61F
2002/30975 (20130101); A61F 2002/30616 (20130101); A61F
2/30744 (20130101); A61F 2002/30331 (20130101); A61F
2002/4638 (20130101); A61F 2002/30708 (20130101); A61F
2002/30822 (20130101) |
Current International
Class: |
A61F
2/38 (20060101) |
Field of
Search: |
;623/20.32-20.34,20.15,20.16,20.27,20.28,20.29,20.31,20.35,20.36 |
References Cited
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Primary Examiner: Prebilic; Paul
Attorney, Agent or Firm: Baker & Daniels LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This patent application is a divisional of U.S. patent application
Ser. No. 10/370,154, filed Feb. 19, 2003, and claims the benefit
under 35 U.S.C. .sctn.119(e) of U.S. Provisional Patent Application
Serial No. 60/358,174, filed Feb. 20, 2002.
Claims
We claim:
1. A method of performing knee arthroplasty comprising the steps
of: (a) providing a multi-piece tibial component, the tibial
component including (i) a tibial base having an inferior surface
for engagement with a prepared surface at the proximal end of a
tibia and a passageway extending through the base, the passageway
including an open proximal end, an open distal end, and a portion
which tapers inwardly in a distal direction, the tibial base
further including an enlarged threaded aperture adjacent said
superior surface and defining a shoulder extending outwardly from
the portion which tapers inwardly, and (ii) a tibial stem including
a tapered extension shaped to snugly engage the tapered portion of
the passageway and a threaded flange portion shaped to threadably
engage the enlarged threaded aperture of the tibial base, the
threaded flange positioned proximal of the tapered extension; (b)
preparing the proximal end of a tibia including forming a cavity
along the intramedullary canal of the tibia; (c) positioning the
tibial base on the prepared tibia proximal end; (d) thereafter
positioning the tibial stem through the passageway in the tibial
base, wherein a portion of the tibial stem is retained within the
passageway and a portion of the tibial stem extends distally from
the open distal end of the passageway and into the prepared cavity;
and (e) securing the tibial base and the tibial stem together by
threadably engaging the threaded flange portion of the tibial stem
with the threaded aperture of the tibial base, such that the
tapered extension of the tibial stem is lockingly engaged with the
passageway of the tibial base, said step of securing the tibial
base including leaving a gap between a distal side of the threaded
flange and a proximal surface of the shoulder to ensure that the
threadably engaging step effects locking engagement of the tapered
extension and tibial base.
2. The method of claim 1 wherein the tibial base has inwardly
facing threads and the tibial stem has outwardly facing threads
proximally of the tapered extension and further including the step
of engaging the outwardly facing threads to the inwardly facing
threads.
3. The method of claim 2 wherein the tibial component further
includes an insert engageable with the base, the insert having a
passageway and the tibial stem extension having a threaded cavity
and further extending a screw through the insert passageway and
engaging it in the extension threaded cavity.
4. A method for anchoring a tibial implant to a proximal tibia, the
method comprising the steps of: seating a tibial plate on the
proximal tibia, the tibial plate having a passageway extending
therethrough, the passageway having an open proximal end and an
open distal end, the open proximal end having a threaded aperture
formed therein, the threaded aperture defining a shoulder extending
outwardly from the passageway; extending an elongated member
through the tibial plate and into the tibia after the step of
seating a tibial plate on the proximal tibia, the elongated member
having a proximal end with a threaded flange portion and a distal
end, wherein the proximal end of the elongated member is positioned
within the passageway and the distal end of the elongated member
extends distally from the open distal end of the passageway;
securing the elongated member to the tibial plate by threadably
engaging the threaded flange portion of the elongated member with
the threaded aperture of the tibial plate, said step of securing
effecting a taper lock between a tapered portion of the elongated
member and a correspondingly tapered portion of the passageway,
such that a gap remains between a distal side of the threaded
flange and a proximal surface of the shoulder, whereby firm locking
engagement of the tapered extension and tibial base is ensured by
said threadably engaging step; mounting a tibio-femoral insert to
the tibial plate; and inserting a screw through the tibio-femoral
insert and into threaded engagement with a socket formed in the
elongated member to retain the tibio-femoral insert on the tibial
plate.
5. The method of claim 4, wherein extending an elongated member
through the tibial plate includes threadably engaging the elongated
member with the tibial plate.
Description
BACKGROUND OF THE INVENTION
In performing knee arthroplasty with conventional knee prostheses,
it has been necessary to form large incisions in order to
accommodate the preparation of the femur to receive the prosthesis
and to accommodate the reception of a fairly large prosthesis into
the incised femur for implantation on the prepared distal end of
the femur. As is appreciated by those skilled in the art, it is
desirable to minimize the size of any incision as the smaller the
incision, the more rapidly the patient may recover. Prior art
prostheses formed with a single piece metal component having both
left and right condylar portions integral with the patellar flange
area require large incisions in order to accommodate implantation
in the prepared femur. In contrast, under the present invention,
through the use of multiple pieces for the femoral component, it is
possible to greatly reduce the size of any such incision, thereby
reducing the amount of damage to soft tissue from any such
arthroplasty and speeding the time of recovery. Similarly, it is
desirable to minimize the size of any incision in the tibia during
any implantation of the tibial component.
SUMMARY OF THE INVENTION
The present invention is directed to a prosthesis for use in knee
arthroplasty including total knee arthroplasty which is minimally
invasive to the patient and to a method for performing surgery
using such prosthesis including the femoral and tibial components
thereof. Under the invention, the femoral component and,
preferably, the tibial component are manufactured in at least two
and possibly three or more pieces. However, it is possible that the
tibial component could be a single piece, monoblock construction as
well as modular multipiece construction. In both the single piece
and multipiece construction, there is also provided a plastic
articular surface insert piece. The pieces are designed to be
assembled together following insertion into the knee. This allows
total knee arthroplasty to be performed through very small
incisions, as small as three inches, in each of the distal end of
the femur and proximal end of the tibia. Following insertion, the
pieces of the femoral component implanted at the distal end of the
femur are joined together with a locking mechanism to form the
modular femoral component and the pieces of the tibial component
implanted at the proximal end of the tibia are assembled to form
the modular tibial component.
Femoral Component
The femoral component may have three component pieces for a
cruciate retaining design and two component pieces for a cruciate
sacrificing design. It may be manufactured as two or three separate
pieces or manufactured as a single unitary member which is
subsequently cut or otherwise divided into two or three separate
pieces. The pieces are provided with a locking joint for retaining
the pieces together following insertion in distal end of the femur.
The locking joint for the pieces is placed at the area of low
patella/femoral contact, a low stress area of the femur. This
corresponds to the anterior chamfer cut of a routine total knee
arthroplasty and the area can be easily reinforced to accommodate
the additional thickness of the locking joint. Various locking
mechanisms may be employed for joining the pieces together
including screws or a transverse locking pin which may be inserted
from the medial side and/or lateral side. The locking mechanisms of
whatever type lock the component pieces together into a solid
assembled prosthesis. The prosthesis will be additionally
reinforced by the underlying bone and/or cement fixation and will
produce a durable construction. The patellar flange and the area of
any joint between assembled components which may be contacted by
the patella should be smoothed and, possibly, recessed to prevent
premature wear of the patellar member as it tracks over the joint
in the femoral component.
Tibial Component
The tibial component preferably has two pieces, namely, a tibial
base and a tibial stem. It is also inserted in pieces from the
side. It may also be a monoblock, one-piece tibial component with
pegged or short stem fixation. The tibial base may have of a flat
baseplate with anterior and posterior dovetails and may have a
tapered transverse keel. The other piece of the tibial component is
a modular stem which is inserted from the top after the baseplate
is inserted. This design allows the components to be inserted
through the minimal incision and still have long term stability.
The stem is preferably fixed with a reverse Morse taper so that it
can be driven through the baseplate like a spike.
Patellar Component
A standard conforming dome configuration patellar component is
Utilized, with the main difference being its method of insertion.
It may be inserted without everting the patella. This is
accomplished with the use of special instrumentation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of one embodiment of femoral component
showing the medial condyle as a separate piece from the remainder
of the femoral component.
FIG. 2 is a perspective view of a second embodiment of femoral
component showing the lateral condyle as a separate piece from the
remainder of the femoral component.
FIG. 2A is a sectional view showing a patellar member engaged to
the articulating surface of the patellar femoral flange piece.
FIG. 3 is a perspective view of another embodiment of femoral
component showing both the medial condyle and the lateral condyle
as separate pieces from the patellar femoral flange piece of the
femoral component.
FIG. 4 is a perspective view showing the patellar femoral flange
piece of FIG. 3 taken from a different angle.
FIG. 5 is a perspective view of an embodiment of femoral component
showing the patellar femoral flange piece as a separate piece from
the remainder of the femoral component.
FIG. 6 is a front view of the embodiment of the femoral component
of FIG. 5.
FIG. 7 is a side view of the embodiment of the femoral component of
FIG. 5.
FIG. 8 is a sectional view taken through line 8-8 of FIG. 6.
FIG. 9 is a sectional view taken through line 9-9 of FIG. 6.
FIGS. 10 and 11 are perspective views of other embodiments of the
femoral component showing the patellar femoral flange piece as a
separate piece from the remainder of the femoral component.
FIG. 11A is a view similar to FIG. 9 for the embodiment of FIG.
11.
FIG. 11 B is a sectional view through line 11B-11B of FIG. 11A.
FIG. 12 is a perspective view of another embodiment of femoral
component showing the patellar femoral flange piece as a separate
piece from the remainder of the femoral component and showing one
form of design for connecting the patellar femoral flange piece to
the remainder of the femoral component.
FIG. 13 is an enlarged view of the circled portion of FIG. 12.
FIG. 14 is a perspective view of an embodiment of femoral component
showing the lateral condyle as a separate piece from the remainder
of the femoral component.
FIG. 15 is an enlarged view of the circled portion of FIG. 14.
FIG. 16 is a perspective view of another embodiment of femoral
component showing the patellar femoral flange piece as a separate
piece from the remainder of the femoral component.
FIG. 17 is an enlarged view of the circled portion of FIG. 16.
FIG. 18 is a perspective view of the tibial component showing the
stem portion thereof as a separate piece from the base.
FIG. 18A is a view similar to FIG. 18 with the added feature of a
stem extension as part of the tibial component.
FIG. 19 is a sectional view of another, embodiment of tibial
component showing the stem portion thereof as a separate piece from
the base.
FIG. 20 is a perspective view of another embodiment of tibial
component showing the stem portion thereof as a separate piece from
the base.
FIG. 21 is a side view of the tibial component of FIG. 20 showing
its implantation in the proximal end of a prepared tibia.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, there is shown one embodiment of femoral
component generally designated by the numeral 10. The femoral
component includes a first piece 12 having a patellar flange
portion 14 and an integral, unitary lateral condyle portion 16
extending therefrom. A prior art femoral component would also have
an integral, unitary medial condyle on the opposite side from the
lateral condyle portion 16. Under the present invention, there is
provided, as a separate piece, a medial condyle piece 18 intended
to be assembled to the first piece 12 following implantation of
both the first piece 12 and the medial condyle piece 18 in the
patient. The assembly mechanism or locking joint for securing the
medial condyle piece 18 to the first piece 12 will be hereinafter
described.
As shown in FIG. 1, the medial condyle piece 18 is provided with a
recess 15 for receiving bone cement and a pair of fixation pins 17.
The first piece 12 may also be provided with one or more recesses
and fixation pins. If it is desired to have a prosthesis for
implantation without bone cement, the recesses such as the recess
15 can be replaced by one of several types of porous surfaces well
known in the art for bone in-growth.
Referring to FIG. 2, there is shown a second embodiment of a
femoral component 20 having a first piece 22 with a patellar
femoral flange portion 24 and an integral, unitary medial condyle
portion 26. The second component of this embodiment is a lateral
condyle piece 28 which may be joined with the first piece 22
following implantation of both the first piece 22 and the lateral
condyle piece 28 in the femur of the patient.
FIG. 2A shows a sectional view of patellar member P in contact with
the articulating surface of the patellar femoral flange portion
24.
FIG. 3 shows yet another embodiment of a three-piece femoral
component 30. Under this embodiment, there is provided a patellar
femoral flange piece 32, a second piece 34 which is a medial
condyle piece and a third piece 36 which is a lateral condyle piece
assuming, of course, implantation in the right knee of a patient.
If the femoral component 30 were implanted in the left knee of a
patient, the second piece 34 would be the lateral condyle piece and
the third piece 36 would be the medial condyle piece. Each of the
second piece 34 and the third piece 36 are joined to the patellar
femoral flange piece 32 following insertion in the patient's femur
by use of a locking joint to be hereinafter described.
All three of the pieces of the femoral component may be provided
with fixation pins 37 and recesses 35 if intended for use with bone
cement or a porous surface if intended for non-cemented
implantation.
FIG. 4 is a perspective view of the patellar femoral flange piece
of FIG. 3 taken from a different angle.
The femoral components 10, 20 and 30 of FIGS. 1 through 3 could be
used for implantation in either knee. The foregoing description for
each of the femoral components 10, 20 and 30 is based on the
assumption of implantation in the right knee. If they were used for
implantation in the left knee, the pieces identified by the
numerals 18 and 34 would be lateral condyle pieces, the pieces
identified by the numerals 28 and 36 would be medial condyle
pieces, the portion identified by the numeral 16 would be a medial
condyle portion and the portion identified by the numeral 26 would
be a lateral condyle portion.
Referring to FIGS. 5, 6, 7, 8 and 9, there is shown an embodiment
of femoral component 40 having two pieces, namely, a patellar
femoral flange piece 41 and a condylar piece 42. The patellar
femoral flange piece 41 has a patellar engaging surface 43 shaped
to allow anatomical tracking of a natural or prosthetic patella P.
As shown in FIG. 5, the patellar femoral flange piece 41 has a
superior bone engaging surface 46 and a patellar engaging surface
43 defining a portion of an inferior articulating surface. The
patellar femoral flange piece 41 extends from an inferior end 45 to
a leading end 48 which is contoured to engage the condylar piece
42. The condylar piece 42 includes a first condylar portion 50 and
a second condylar portion 52 and extends from an engagement end 54
contoured to receive the leading end 48 of the patellar flange 41
to a posterior end 55. As will be appreciated by those skilled in
the art, the femoral component 40 could be used for implantation in
either a right knee or left knee and the first and 'second condylar
portions will be either lateral or medial facing depending upon the
knee in which the femoral component 40 is implanted.
The condylar piece 42 has a superior bone engaging surface with a
series of bone engaging flats 60, 61, 62 and 63 disposed at varying
angles consistent with cuts made in preparing the distal end of the
femur to receive the condylar piece 42. If desired, the superior
bone engaging surface 46 of the patellar flange piece 41 and the
superior bone engaging surfaces 60, 61, 62 and 63 of the condylar
piece 42 may be formed with recesses for receiving bone cement or
porous surfaces for bone ingrowth and may also be provided with
fixation pins.
The condylar piece 42 in the embodiment of FIGS. 5-9 is formed as a
single unitary piece for implantation. As such, the first condylar
portion 50 and the second condylar portion 52 are joined together
with a posterior cam 56 which may be formed integral with or welded
or otherwise joined to the first and second condylar portions 50,
52. The engagement end 54 of the condylar piece 42 also has the
first and second condylar portions 50, 52 joined together by a
laterally extending cross member 57. As will be appreciated by
those skilled in the art, the use of the posterior cam 56 will
result in sacrificing of the posterior cruciate ligament. As will
be appreciated, in those cases where it may be necessary to
sacrifice the posterior cruciate ligament for other reasons, the
feature of having both a posterior cam 56 and a cross member 57 for
joining the first and second condylar pieces 50, 52 will provide
great rigidity to the condylar piece 42.
As can be seen in FIGS. 5, 7 and 9, the cross member 57 has a
superior bone engaging surface 57A and a medial surface 57B
approximately midway between the superior bone engaging surface 57A
and the articulating surfaces 51 and 53 of the first condylar
portion 50 and second condylar portion 52, respectively. On the
posterior side of the cross member 57 is a posterior wall surface
57C extending between the superior bone engaging surface 57A and
the surface 57B. Opposite the posterior surface 57C is a fourth
surface 57D which will engage a corresponding surface to be
described of the patellar femoral flange piece 41.
The engagement ends 54 for each of the first and second condylar
portions 50, 52 each follows a curved path defined by sidewall
engagement surface 54A as shown in FIGS. 5 and 6. Each of the
curved engagement wall surfaces 54A extends to the general area
defined by the posterior wall surface 57C of cross member 57. (See
FIG. 5). The positioning of the joint defined by the surfaces 54A
of the condylar piece 42 and the mating surfaces of the patellar
femoral flange piece 41 is important and should be in the vicinity
of the normal femoral tide mark which is a low stress area of
contact by sliding engagement of the patella. By providing the
joint in this area, the prosthesis has great ability to function as
desired with no separation of the patellar femoral flange piece 41
from the condylar piece 42 following implantation. The normal
femoral tide mark corresponds to the area of the inferior chamfer
cut of a routine total knee arthroplasty.
The patellar femoral flange piece leading end 48 has a pair of
curved engagement surfaces 64 following a contour for mating
engagement with the respective surfaces 54A of the condylar piece
42. Centrally positioned between the curved engagement surfaces 64
is a central wall surface 65 which, when the patellar femoral
flange piece 41 is engaged to the condylar piece 42, lies in
substantially the same plane as the surface 57C of cross member 57.
(See FIG. 9). The central wall surface 65 extends superiorly from
the patellar engaging surface 43 to a ledge 66 intended to rest
upon the surface 57B of cross member 57. The ledge 66 extends away
from the central wall surface 65 to a central engagement surface 67
which is intended to engage the surface 57D of cross member 57. A
bone engaging surface 68 extends from the central engagement
surface 67 toward the anterior end 45.
As shown in FIGS. 6, 7 and 9, the condylar piece 42 may be secured
to the patellar femoral flange piece 41 by means of screws 68
extending through apertures 69 extending through engagement end
area 54 of the respective first and second condylar portions 50 and
52, through the engagement end surfaces 54A and into aligned
threaded apertures 71 extending inwardly from the curved engagement
surfaces 64 of the patellar femoral flange piece 41.
Referring to FIG. 8, there is shown the articulating surface
defined by the patellar engaging surface 43 of the patellar femoral
flange piece 41 and the articulating surface 59 of the condylar
piece 42 in the area of the joint defined by the mating surface 54A
of the condylar piece 42 and surface 64 of the patellar femoral
flange piece 41. As can be seen in FIG. 8, the respective surfaces
43 and 59 are recessed slightly at such joint to provide a slight
dip 73 so that any movement of the patellar member P over such
joint will leave a slight gap between the surface of the patellar
member P and the surfaces 43 and 59 at the dip 73.
The presence of the gap and the dip 73 has a two-fold advantage. It
reduces the amount of stress in that area of the joint defined by
the mating surfaces 54A and 64 at the surfaces 43 and 59.
Additionally, if there is a slight mismating of the patellar
femoral flange piece 41 relative to the condylar piece 42 such that
one of the surfaces 43 or 59 were slightly high or lower than
intended for precise fixation, the presence of the dip 73 will
serve to prevent the patellar member P from contacting and being
subjected to premature wear by a sharp corner of the higher
piece.
Referring to FIG. 10, there is shown a further embodiment similar
to that of FIGS. 5 through 9 but one in which there is provided a
condylar piece 42A having the first condylar portion 50A is joined
to the second condylar portion 52A only by a posterior cam 56A.
Under this embodiment, the patellar femoral flange piece 41A has a
central wall surface 65A centrally positioned between curved
engagement surfaces 64A. The central wall surface 65A extends
throughout the thickness of the patellar femoral flange piece 41A.
Therefore, there is no ledge similar to the ledge 66 shown in FIG.
5. All other features of the embodiment of FIG. 10 are similar to
corresponding features of the embodiment of FIGS. 5, 6, 7, 8 and
9.
Referring to FIGS. 11, 11A and 11B, there is shown a further
embodiment of femoral component 40B similar to that of FIGS. 5
through 9 but one in which there is provided a condylar piece 42B
having the first condylar portion 50B joined to the second condylar
portion 52B only by a cross member 57B and a modified connector
means for fastening the condylar piece 42B to the patellar femoral
flange piece 41 B.
The cross member 57B is provided with an extension 130 extending
superiorly (i.e., downwardly as viewed in FIGS. 11 and 11A) from
the cross member 57B. Both the cross member 57B and the extension
130 are provided with a common dovetail slot 132. The extension 130
is an integral unitary part of the cross member 57B and, in cross
section, has a generally semicircular cross sectional configuration
with the side facing the patellar femoral flange piece 41 B having
a pair of flat faces on opposite sides of the dovetail slot
132.
The patellar femoral flange piece 41 B, has a configuration similar
to that of the patellar femoral flange piece 41 as shown in FIG. 5,
including a central wall surface 65B extending from a patellar
engaging surface 43B, a ledge 66B and a central engagement surface
67B. A bone engaging surface 68B extends from the central
engagement surface 67B toward the anterior end 45B. Extending
superiorly from the bone engaging surface 68B is an extension 134
having a dovetail 136 sized to be snugly received in the dovetail
slot 132 of the extension 130 with conforming mating surfaces. The
dovetail 136 and dovetail slot 132 could have other crossectional
configurations from that shown in FIGS. 11, 11A and 11B such as
circular or rectangular. As will be appreciated and as can be seen
from FIGS. 11A and 11B, the dovetail 136 is an integral unitary
part of the extension 134; however, it extends outwardly from the
surface 67B and upwardly from the surface 68B to join with surface
66B.
The respective extensions 130 of the condylar piece 42B and 134 of
the patellar femoral flange piece 41B, when joined together with
the dovetail 136 positioned in the dovetail slot 132 will cooperate
to define a substantially cylindrical configuration; however, if
desired, a different configuration, such as square, rectangular or
rounded, could be utilized.
Preparatory to implantation of the condylar member 42B and patellar
femoral flange piece 41B, an aperture is drilled or otherwise
formed in the femur of sufficient size to receive the extensions
130 and 134.
Following positioning of the condylar piece 42B in the prepared
femur with its extension 130 positioned in the prepared bone
cavity, the patellar femoral flange piece 41B is moved therein, the
dovetail 136 is aligned with the dovetail slot 132 and the patellar
femoral flange piece 41B is moved toward the prepared femur with
the dovetail 136 sliding through the dovetail slot 132 until the
surface 66B of the patellar femoral flange piece 41B contacts the
anterior surface of cross member 57B. Desirably, bone cement will
be positioned in the prepared aperture of the femur to engage the
adjoined extensions 130 and 134.
Referring to FIGS. 12 and 13, there is shown an embodiment of a
two-piece femoral component 74 with a first piece 75 of a patellar
flange area having a patella engagement surface 76 and a second
piece 77 having a medial condyle portion 78 and a lateral condyle
portion 79 formed as an integral unitary piece. The second piece 77
has a series of flats 96, 97, 98, 99 for engagement with a prepared
distal end of a femur.
The first piece 75 has an abutment wall 81 extending from the
patella engagement surface 76 and positioned to engage a
corresponding abutment wall 82 of the second piece 77. The line of
juncture between the abutment wall 81 of the first piece 75 and the
abutment wall 82 of the second piece 77 is in the area of low
patella/femoral contact which is a low stress area of the femur.
The abutment wall 81 extends only partially through the thickness
of the first piece 75. The abutment wall 81 joins with a second
Wall 83 disposed substantially at right angles thereto (See FIG.
13). The second wall 83 extends to an end wall 84. Extending
outwardly from the end wall 84 toward the plane defined by the
abutment wall 81 is a ledge 85 having an upper surface 86 with a
tongue or dovetail 87 projecting upwardly therefrom. The tongue 87
and upper surface 86 extend throughout the breadth of the first
piece 75. The tongue 87 is provided with a pair of reverse taper
surfaces 88 which flare outwardly from one another in a direction
away from the upper surface 86.
Extending outwardly from the abutment wall 82 of the second piece
77 is an insert ledge 90 having an upper surface for mating
engagement with the second wall 83 of the first piece 75. The lower
portion of the insert ledge 90 opposite the upper surface has
formed therein a dovetail groove 92 extending the full breadth of
the second piece 77 and sized to receive the tongue 87 of the first
piece 75. As can be seen from FIG. 13, when the first piece 75 and
second piece 77 are joined together, there will remain a gap 93
between the end wall 84 of the first piece 75 and the end of the
insert ledge 90 of the second piece 77. In order to prevent the
engaged first piece 75 and second piece 77 from moving laterally
relative to one another, there is provided a tapered pin 94 which
may be driven into the gap 93 to function as a wedge putting the
tongue 87 into compression in the dovetail groove 92 formed in the
lower surface of the insert ledge 90.
Referring to FIGS. 14 and 15, there is provided another embodiment
of prosthesis. 100 with a first piece 101 having both a patellar
flange area 102 and an integral, unitary lateral condyle portion
103. The prosthesis 100 also has a second piece 104 which is a
medial condyle piece. The first piece 101 has a first abutment wall
105 extending generally laterally and a second abutment wall 106
extending generally longitudinally with a curved wall section 107
joining the first abutment wall 105 and the second abutment wall
106. Protruding outwardly from the second abutment wall 106 is a
projection 110 having sidewalls 111 (only one of which is shown)
tapering inwardly toward one another as they extend outwardly from
the second abutment wall 106 and end walls 112 tapering inwardly
toward one another as they extend outwardly from the second
abutment wall 106. The tapering sidewalls 111 and end walls 112 are
joined by an outer wall 113 substantially parallel with the second
abutment wall 106. The projection 110 is integral and unitary with
the remainder of the first piece 101 and may be formed by a milling
process, for example. A threaded aperture 114 extends through the
projection 110 from the outer wall 113 and, preferably, extends
into the adjacent portion of the first piece 101.
The second piece 104 has a first abutment wall 115 positioned to
engage the first abutment wall 105 of the first piece 101, a second
abutment wall 116 positioned and sized to engage the second
abutment wall 106 of the first piece 101 and a curved wall 117 for
engagement with the curved wall 107 of the first piece 101. Formed
in the second wall 116 is a recess 118 contoured to snuggly receive
the projection 110 of the first piece 101. A laterally extending
passageway 108 extends through the second piece 104 in alignment
with the threaded aperture 114 of the first piece 101 when the
second piece 104 is engaged thereto.
In order to join the second piece 104 to the first piece 101 there
is provided an elongated screw 120 having a threaded section 121
for mating with the threads of the threaded aperture 114 of the
first piece 101. The screw 120 has a cylindrical section 122 of
larger diameter than the threaded section 121 and sized to be
snugly received in the passageway 108 of the second piece. The
screw 120 has an enlarged head 123 sized to fit in a countersunk
area of the passageway 108 at the outer edge of the second piece
104.
Referring to FIGS. 16 and 17, there is shown a two-piece femoral
component 140 including a first piece 141 having both a lateral
condyle 142 and a medial condyle 143 formed as part of an integral,
unitary piece. The second piece 144 defines a patellar flange area
of the femoral component 140. The second piece 144 has a contoured
abutment wall 145 including a first flat surface 145A extending
inwardly from the lateral side, a second flat surface 145B
extending inwardly from the medial side of the second piece 144 and
a recess defined by first and second side walls 145C and a bottom
wall 145D. The sidewalls 145C taper inwardly toward one another as
they extend from their respective flat surfaces 145A and 145B to
the bottom 145D. Preferably, the bottom wall 145D is curved;
however, it could be flat.
The first piece 141 is provided with an abutment wall 146 having a
contour to be snuggly engaged to the abutment wall 145 of the
second piece 144. As such, the abutment wall 146 includes a tongue
147 contoured to fit snuggly in the groove defined by sidewalls
145C and bottom wall 145D of the second piece 144. The tongue 147
is defined by sidewalls 146C, 146C and an end wall 146D contoured
to snuggly engaged the wall 145D forming the bottom of the groove
of the second piece 144. The walls 146C, 146C taper inwardly toward
one another as they extend toward the wall 146D and snuggly engage
the tapered sidewalls 145C of the second piece 144.
The second piece 144 has formed therein a first passageway 148A
which extends inwardly from the lateral edge and is substantially
parallel to the first flat surface 145A and a second passageway
148B which extends inwardly from the medial edge and is
substantially parallel to the second flat surface 145B. A
passageway 149 is formed in the tongue 147 in a position to be
aligned with the passageways 148A and 148B when the first piece 141
is engaged to the second piece 144, with the tongue 147 fitting in
the groove. A pin 150 may be inserted through the passageway 148B,
the passageway 149 and the passageway 148A to secure the first
piece 141 to the second piece 144. The pin 150 could be cylindrical
and press fit into the respective passageways 148A, 148B and 149
assuming the passageways were cylindrical or could be tapered
assuming such passageways had the appropriate taper. Additionally,
one of the passageways, passageway 148A, for example, could be
threaded, in which case the pin 150 would have a threaded end for
engagement therewith.
In each of the embodiments, the respective lines of juncture
between abutting walls of the assembled pieces have been selected
to be located generally in the area of the normal femoral tidemark
which is a low stress area.
Referring now to FIG. 18, there is shown a tibial component
generally designated by the numeral 161. The tibial component 161
includes a tibial base 162 and a tibial stem 163. The tibial base
162 has an inferior surface 164 intended to engage the prepared
proximal end of the tibia of the patient and a superior surface
(not shown) to which may be affixed a plastic insert contoured to
be engaged by the condylar portions of a femoral component. The
plastic insert may have one of a number of well known mechanisms
for being attached to the tibial base 162 such as a dove tail
locking mechanism, for example. The plastic insert may be inserted
either laterally or proximally depending on the specific design of
the tibial base and the condition of the patient as determined by
the surgeon. Extending distally from the inferior surface 164 is a
base extension 165 having a generally cylindrical shape but with a
pair of fixation wings or fins 166 extending outwardly from the
cylindrical portion of the base extension 165. A platform 167 is
raised from the inferior surface 164 and follows a contour
encircling the base extension 165 including the wings 166. The
wings 166 function as fixation fins for maintaining the tibial base
162 in a fixed rotational position when implanted on the prepared
proximal end of the tibia. The tibial base 162 is provided with a
notch 168 to accommodate the posterior cruciate ligament and a
plurality of apertures 169 for receiving screws for engagement to
an augmentation block, if one is needed, or for securing the tibial
base 162 to the proximal end of a prepared tibia.
The tibial base 162 has a central passageway 170 extending from the
superior surface 164 and through the cylindrical portion of the
base extension 165. That portion of the central passageway 170 in
the base extension 165 has wall surface which flares outwardly
frusto conically and defines a Morse taper cavity 295 as it
approaches the end of the base extension 165. A recess defining a
notch 240 is formed in the end of the base extension 165. That
portion of the passageway adjacent the superior surface has a
diameter sized to receive a screw 158 and a countersunk area 297 to
receive the enlarged head of such screw 158.
The tibial stem 163 is provided with a pair of wings or fixation
fins 171 which, when the tibial stem 163 is engaged to the
extension 165, will be aligned with and forming extensions of the
respective wings or fins 166 of the tibial base 162. The tibial
stem 163 is provided with a Morse taper extension 298 sized to be
snugly received in the Morse taper cavity 295 of the tibial base
162. A shoulder 262 extends outwardly from the Morse taper
extension 298. A raised tab 242 extends proximally from the
shoulder 202 and is sized to fit snugly in the notch 210 and, when
so positioned, assures alignment of the fixation fins 171 of the
tibial stem 163 with the fins 166 of the tibial base 162.
A threaded passageway 172 is formed in the Morse taper extension
298 and is aligned with the central passageway 170 when the tibial
stem 163 is engaged to the extension 165. The tibial stem 163 is
supported on the tibial base 162 by the screw 158 extending through
the central passageway 170 of the tibial base 162 and engaged to
the threaded passageway 172. A plug 244 is engaged in the distal
end of the tibial stem 163 to prevent blood or other contaminates
from entering the threaded passageway 172. The plug 244 may be
secured to the tibial stem 163 by means of a threaded extension
engaging the threaded passageway 172.
FIG. 18A shows an embodiment similar to FIG. 18 but in which there
is provided a stem extension 250 but not a plug such as the plug
244 of FIG. 18. The stem extension 250 is provided with a Morse
taper 252 at its proximal end 253. A threaded recess 254 extends
distally from the proximal end and has a size smaller than the
threaded passageway 172. A threaded screw 258 sized to engage the
threaded recess 254 secures the stem extension 250 and the tibial
stem 163 to the tibial base 162. The threaded screw 258 is small
enough to pass through the threaded passageway 172 without engaging
its threads.
The distal end of the tibial stem 163 has a cavity 260 tapering
outwardly in a distal direction and defining a Morse taper sized to
snuggly receive the Morse taper 252 of the stem extension 250. Two
grooves 270 are formed in the tibial stem 163, on opposite sides,
distally spaced from the shoulder 262. The purpose of the grooves
270 is to permit engagement and support for the tibial stem during
implantation as will be discussed hereinafter.
Referring to FIG. 19, there is a shown in section a modified
embodiment of tibial component 200. Under this embodiment there is
provided a tibial base 202, a tibial stem 204 and a plastic insert
206 for engagement with the tibial base 202. The tibial base, as
shown in FIG. 19, has a raised wall 208 and a flat superior surface
210. The tibial base 202 has an inferior surface 212 intended to
engage the prepared proximal end of the tibia of the patient. A
centrally positioned short extension 213 extends from the inferior
surface 212.
Extending through the tibial base 202 including the extension 213
is a passageway 214. That portion of the passageway 214 adjacent
the inferior surface 210 is enlarged from the remainder of the
passageway and is provided with inwardly facing threads 215 in the
area adjacent the inferior surface 210. That portion of the
passageway 214 extending away from the threads 215 is tapered to
define a Morse taper cavity 216 throughout the remainder of the
thickness of the tibial base 202 including the stem 213.
The tibial stem 204 is provided with an enlarged threaded flange
220 sized to engage the threads 215 of the tibial base 202.
Extending from the flange 220 is a Morse taper extension 222 sized
and contoured to be snuggly received in the Morse taper cavity 216.
Extending inwardly from the inferior surface 210 is a cavity
defined by a series of flats 224 which cooperate to define a
hexagon or other conveniently shaped cavity for receipt of a tool
for engagement therein for threading the threaded flange 220 into
the threads 215.
Extending from the cavity defined by the flats 224 is a threaded
aperture 225. Extending distally from the Morse taper extension 222
is a reduced size cylindrical extension 227.
The plastic insert 206 has molded therein a metal insert 230 having
an enlarged flange 232 to ensure its firm engagement to the insert
206. The insert 206 is provided with a passageway 234 sized to
receive a screw 236 including its enlarged head 238. The metal
insert 230 is provided with a passageway 240 sized to receive the
threaded portion of the screw 236 but smaller than the enlarged
head 238. Following engagement of the tibial stem 204 to the tibial
base 202, the plastic insert 206 is positioned on the inferior
surface 210 within the upwardly extending wall 208. The screw 236
is then engaged to the threaded aperture 225 to secure the plastic
insert 206 thereto.
In the surgical procedure for implanting the tibial component 200,
the proximal end of the tibia is prepared by cutting a flat surface
to receive the inferior surface 212 of the tibial base 202 and a
cavity is drilled in the intramedullary canal of the tibia to
receive the stem 204. The tibial base 202 is positioned on the
prepared flat surface with the extension 213 positioned in the
cavity. The tibial stem 204 is then positioned in the passageway
214 with the cylindrical extension 227 passing through the Morse
taper cavity 216 and into the cavity of the intramedullary canal.
Using a tool engaged to the flats 224, the stem is threadedly
engaged to the threads 215 and the base 202 to cause the Morse
taper extension 222 to firmly engage the Morse taper cavity 216. As
may be seen in FIG. 19, the tibial stem 204 is so contoured
relative to the tibial base 202, that a gap 229 will remain between
the distal side of the flange 220 and the surface of the tibial
base 202 extending radially outwardly from the Morse taper cavity
216. This ensures that the Morse taper extension 222 will firmly
engage the Morse taper cavity 216 upon threaded engagement of the
threaded flange 220 to the threads 215.
Referring now to FIGS. 20 and 21, there is shown another embodiment
of tibial component 180 along with a tool 195 for use in implanting
such tibial component in the proximal end of a prepared tibia T.
The tibial component 180 includes a tibial base 181, a tibial stem
182 and a plastic insert 179 engaged to the tibial base 181. The
tibial base 181 has an inferior surface 183 intended to engage the
prepared proximal end of the tibia T and a superior surface 184 to
which may be affixed a plastic insert 179 contoured to be engaged
by a femoral component. The tibial base 181 has raised areas 185
along the anterior and posterior edges. Each of the raised areas is
provided with an undercut wall surface 186 defining grooves for
receiving and retaining the plastic insert 179.
Extending distally from the inferior surface 183 is an extension
187. The tibial base 181 has a central passageway 188 extending
from the superior surface 184 and through the extension 187. The
extension 187 and the passageway 188 may be disposed at an angle of
up to 10.degree. relative to a line perpendicular to the superior
surface 184 in order to accommodate the anatomy of the patient.
The tibial stem 182 is provided with a recess 190 sized and
positioned to become an extension of the passageway 188 of the
tibial base 181. The recess 190 may be threaded for engagement by a
threaded screw 196 extending through the plastic insert 179 and its
articular surface and through the passageway 188 to join the tibial
stem 182 to the tibial base 181. As shown in FIG. 21, the distal
end 188A of the passageway 188 may be tapered to define a Morse
taper cavity. The tibial stem 182 is also provided, at its proximal
end, with a Morse taper extension 197 sized to snugly engage the
Morse taper cavity at the distal end 188A of the passageway 188.
The tibial stem 182 is also provided with a plurality of outwardly
facing grooves 189 to assist in fixation.
In preparing the proximal end of the tibia T to receive the tibial
component 180, the proximal end T1 of the tibia is cut to form
substantially a flat surface. A cavity T2 is formed to receive the
tibial stem 182. Since the cavity T2 may be oversized, the tibial
stem 182 is provided with an annular groove 198 sized to receive
the tines 195A of the tool 195. As can be seen in FIG. 21, with the
tines 195A engaged in the groove 198, the tool 195 can support the
tibial stem 182 at the proper location relative to the prepared
proximal end T1 of the tibia T until such time as the screw 196 is
engaged in the threaded recess 190 to support such tibial stem 182
on the tibial base 181.
In implanting the tibial stem 163 of the embodiment of FIGS. 18 and
18A, a tool similar to the tool 195 may be used to engage the
grooves 270 to support the stem 163 until it is engaged by the
screw 158 or 258.
In each of the embodiments of FIGS. 18, 18A, 19, 20 and 21, it is
preferred that the surface of the tibial base which is to be
contacted by a plastic insert be polished to a high degree, on the
order of four (4) rms or less, to prevent premature wear on the
surface of the plastic insert engaged to the tibial base.
Description of Surgical Procedure
A medial parapatellar incision is made from the superior pole of
the patella to the tibial tuberosity. Medial parapatellar
arthrotomy is made from the inferior edge of the vastus medial is
to the tibial tuberosity. A subvastus or mid vastus arthrotomy may
be utilized, based upon patient anatomy or surgeon experience.
The knee is place in extension and the patella excised without
eversion, using a patellar clamp inserted into the prepatellar
bursa, to prevent damage to the anterior skin.
An extramedullary tibial alignment guide is placed along the medial
or lateral half of the tibia and secured with fixation pins. An
extrameduallary alignment guide of the type disclosed in U.S.
application Ser. No. 09/973,584 filed Oct. 9, 2001, assigned to the
assignee of the present invention and incorporated herein by
reference, is fixed to the femur after performing the
extramedullary alignment procedure, and the distal femoral cut is
made at the appropriate depth and angle of the implant, nominally
6.degree. valgus and 10-12 mm depth of cut. As an alternative, an
intramedullar alignment guide system could be used. This cut is
taken all the way across both distal femoral condyles, rather than
being unicondylar in nature. This cut is made at 90.degree. to the
femoral shaft.
The tibial component is implanted first. The fixation surface is
coated with cement, and the modular tibial stem is driven through
the reverse Morse taper to lock the tibial stem to the bone.
The anterior flange component is then implanted, followed by the
lateral then medial condyles. Once all pieces are loosely assembled
inside the knee and proper alignment is assured, the locking pin is
inserted from the side and rigidly fixes the components together.
Final impaction is then accomplished.
Lastly, the patella is cemented in place.
After all cement has hardened and excess is removed, the final poly
slides in from the side, and is secured with an AP locking clip or
screw, which also helps lock the modular stem in place.
Routine closure is performed, and rapid rehab program
initiated.
The above detailed description of the present invention is given
for explanatory purposes. It will be apparent to those skilled in
the art that numerous changes and modifications can be made without
departing from the scope of the invention.
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